Caption: MODEL RELEASED. Ozone and plant growth experiment. Researchers measuring ozone concentration at ground level in an experiment on the effects of ozone on plant growth. They are using a portable infrared ozone monitor. In the lower atmosphere, ozone is a pollutant gas. The ozone is released from pipes (background, upper left) to be carried across the meadow by the wind. The meadow is part of a diverse conservation area, in which the effects of ozone on a wide variety of plants and soil organisms are studied. Photographed at Keenley Fell, Allendale, Northumberland, UK.